How to calculate what percentage of the area of an object appears in the render view?
In case anyone have a similar problem, I 'kinda' solved the problem using ray-cast. I basically created a for loop that generates ray-casts coming from the camera with destination to the 4 vertices that frame the jersey number. I have to perform this calculation for every object that I think might be between the camera and the body. With this approach I don't really calculate the area but it turns out that it is sufficient for my goal to know that at least one of the ray-casts intercept an object.